expansion port

[Atari_Bill]

Is the 7800 with the expansion port any more desirable than any other?  Are there any incompatibilities between the 3 variations of the units?

[jstrotha0975]

I read somewhere on Atariage that someone was making something that would use the expansion port, but don't ask me what it is or where to find it.

[+-^CrossBow^-]

1 minute ago, jstrotha0975 said:

I read somewhere on Atariage that someone was making something that would use the expansion port, but don't ask me what it is or where to find it.

I believe it was @CPUWIZ who hinted at possible functionality coming for the expansion port and that was why he was stating how easy it wast to install a set of double inline right angle headers to the board to recreate it so to speak. But I've not seen anything regarding it.

 

13 minutes ago, Atari_Bill said:

Is the 7800 with the expansion port any more desirable than any other?  Are there any incompatibilities between the 3 variations of the units?

I would say that this was originally true in that those with expansion ports were more desired as it was thought they were more compatible vs later made units. However, my experience with the 7800 after having seen quite a lot of them now. Is that the expansion ports were installed up to at least the early to mid 1987. I say this because I've seen A1 and A3 series 7800s with the expansion port on them and using newer revision boards designed with the extra timing circuit. In fact, I just finished up a 7800 that was made in late 1987, did not have any socketed chips on it, had the silkscreen for the extra timing components but was bypassing it with a 0Ω resistor (Common on later made 7800s as well), and... it had the expansion port installed? 

 

So honestly you can't use the expansion port as decider for having one that is more compatible or not because it seems Atari slapped them anytime they happen to find one during the 7800s assembly even up to the point they knew it was never likely to be used, it was still getting installed in some 7800s.

 

BTW that 7800 I was talking about actually had a bottom case shell with the opening for its expansion port and... it had an AT84 sticker on it with Atari Inc. Warner Comms on it. I'm pretty sure it was a swap job someone did in the past as for all the odd stuff Atari was doing during that time, I don't see them letting a 7800 go out the door in late '87 with an Atari Inc sticker on it. They would have slapped a different Atari Corp sticker on it instead and likely a new Serial# to match. Very odd combo. I just hope whoever originally purchased it before the current owner got it, didn't pay the AT84 premium pricing? Cause honestly, it was more like an A3 internally with an expansion port.

 

And now that it is pretty common knowledge that disabling the extra timing circuit on those 7800s that have it actually brings back most of the compatibility working again, it is really a none issue at this point.

 

 

[jstrotha0975]

4 minutes ago, -^CrossBow^- said:

I believe it was @CPUWIZ who hinted at possible functionality coming for the expansion port and that was why he was stating how easy it wast to install a set of double inline right angle headers to the board to recreate it so to speak. But I've not seen anything regarding it.

 

I would say that this was originally true in that those with expansion ports were more desired as it was thought they were more compatible vs later made units. However, my experience with the 7800 after having seen quite a lot of them now. Is that the expansion ports were installed up to at least the early to mid 1987. I say this because I've seen A1 and A3 series 7800s with the expansion port on them and using newer revision boards designed with the extra timing circuit. In fact, I just finished up a 7800 that was made in late 1987, did not have any socketed chips on it, had the silkscreen for the extra timing components but was bypassing it with a 0Ω resistor (Common on later made 7800s as well), and... it had the expansion port installed? 

 

So honestly you can't use the expansion port as decider for having one that is more compatible or not because it seems Atari slapped them anytime they happen to find one during the 7800s assembly even up to the point they knew it was never likely to be used, it was still getting installed in some 7800s.

 

BTW that 7800 I was talking about actually had a bottom case shell with the opening for its expansion port and... it had an AT84 sticker on it with Atari Inc. Warner Comms on it. I'm pretty sure it was a swap job someone did in the past as for all the odd stuff Atari was doing during that time, I don't see them letting a 7800 go out the door in late '87 with an Atari Inc sticker on it. They would have slapped a different Atari Corp sticker on it instead and likely a new Serial# to match. Very odd combo. I just hope whoever originally purchased it before the current owner got it, didn't pay the AT84 premium pricing? Cause honestly, it was more like an A3 internally with an expansion port.

 

And now that it is pretty common knowledge that disabling the extra timing circuit on those 7800s that have it actually brings back most of the compatibility working again, it is really a none issue at this point.

 

 

So you're saying not to worry if you don't have a unit with an expansion port? I hope so because I just bought one 2 weeks ago without the expansion port.

[+-^CrossBow^-]

23 minutes ago, jstrotha0975 said:

So you're saying not to worry if you don't have a unit with an expansion port? I hope so because I just bought one 2 weeks ago without the expansion port.

I wouldn't worry about not having one no. If something is ever created that uses it, you can install header pins to that section to create one more or less. Still have to create an opening in the side of case shell but again there isn't anything currently out that uses it.

 

As for compatibility issues it depends but again you can't use whether yours has an expansion port on it as a factor in knowing this.

 

The main compatibility issue with most non expansion port units is the extra timing circuit. It was put in to allow some newer 2600 games to function on the 7800 at the time. The 2 games I know personally affected by this are the 2600 version of Dark Chambers, and the 2600 version of Kung Fu Master. Most 7800s will play these games without issue. However, this extra circuit on the 7800s that needed it, ends up breaking compatibility with quite a few of the more classic release games. Mostly those made by activision. So it is possible to disable that part of the circuit on those 7800s that happen to have it to get those other games working again but at the cost of possibly the 2 other 2600 games I mentioned not working at that point. But there are 7800 versions of those games anyway that I think are considered to be better to play.

 

Honestly there are so many variations of the 7800 that were made and released that it has been a constant challenge to try and document it all to know what is what.

 

 

[+DrVenkman]

If you check the pinout for it, it's really quit limited in functionality. It was only intended for GCC to sell Atari the companion laser disc player. There's a composite video line on it as well as the system audio line. What would have been fun would have been games that use bright, beautiful laserdisc video backgrounds and recorded music overlaid with MARIA sprites. Ah, what could have been ... alas.

[jstrotha0975]

15 minutes ago, DrVenkman said:

If you check the pinout for it, it's really quit limited in functionality. It was only intended for GCC to sell Atari the companion laser disc player. There's a composite video line on it as well as the system audio line. What would have been fun would have been games that use bright, beautiful laserdisc video backgrounds and recorded music overlaid with MARIA sprites. Ah, what could have been ... alas.

Yes, a 7800 laser disc would have been awesome. Probably would have competed better against Nintendo.

[john_q_atari]

1 hour ago, Atari_Bill said:

Is the 7800 with the expansion port any more desirable than any other?  

To some people perhaps, but I would imagine to most people no, and I would wager that most would never notice if there was a difference. Since you are asking, then the answer for you is no it is not more desirable. If for some reason you desired one in the future I am sure you could find one if you looked. I had a 7800 for years without an expansion port and only looked and acquired one with an expansion port this year. I don't think I paid more than the going rate for 7800s that didn't have the port. Since you appear to be looking for opinions I would not recommend paying more just to have a unit with an expansion port. 

[Atari_Bill]

Thanks all!  That’s the info I was looking for!

[Paul Westphal]

On 11/10/2021 at 2:14 PM, DrVenkman said:

If you check the pinout for it, it's really quit limited in functionality. It was only intended for GCC to sell Atari the companion laser disc player. There's a composite video line on it as well as the system audio line. What would have been fun would have been games that use bright, beautiful laserdisc video backgrounds and recorded music overlaid with MARIA sprites. Ah, what could have been ... alas.

Would it be possible to make a plug in composite video adaptor for the expansion port? That would be cool

[Paul Westphal]

Here is some info's on the port, from an old AA thread :

 

What 2600 carts do not work on the 7800?
There are known incompatibilities with some NTSC versions of the 7800. Games that may not work include Robot Tank, Decathlon, Space Shuttle, Time Pilot, Kool-Aid Man and the Supercharger. In short, 7800s manufactured in 1984 seem to be fully compatible, whereas those manufactured later have inconsistent incompatibilities.

 Test decks:
             Serial #                           Board part#
 Deck#        72R4BR-  Country  Expansion port     CO25233-  Board Date
 -----  -------------  -------  --------------  -----------  ----------
   1    AT  8 5037836   Taiwan    Full port       001 REV A       84-25
   2    A1 76 5904610   Taiwan    Full port       002 REV A       87-17
   3    A1 77 5951337   Taiwan    Hole/no pins    002 REV A       87-17
   4    A3 87 5139813   Taiwan    No port         002 REV B       88-28
   5    A3 07 5298641   China     No port         002 REV B       88-30
 

Board part number/revision is taken from the underside of the board, just above the cart slot. The full number always begins with "CO25233." The boards' top side has a different part number, "CO25234," but no revision level is given. Board dates are also taken from the underside of the board, near the Atari logo. The notation is changed a bit to make sorting by date easier. They're really written like "2584" instead of "84-25," which would indicate the twenty-fifth week of 1984.

The carts tested were:

    Decathlon (2 different carts)
    Robot Tank (3)
    Space Shuttle (5)
    Supercharger (2)
    7800 Food Fight

 Results:  "Yes"  = cart works fine.
           "No"   = cart doesn't do a thing.
           "Roll" = cart works, but picture rolls.
           "Lock" = cart plays for a while, then locks up the system.
 
                 Deck #
      Cart          1        2        3        4        5
                 ------   ------   ------   ------   ------
     Decathlon 1    Yes       No       No      Yes      Yes
               2    Yes       No       No      Yes      Yes
    Robot Tank 1    Yes     Roll     Roll     Roll     Roll
               2    Yes      Yes     Roll     Roll      Yes
               3    Yes      Yes     Roll     Roll      Yes
 Space Shuttle 1    Yes      Yes      Yes      Yes      Yes
               2    Yes      Yes      Yes      Yes      Yes
               3    Yes     Roll     Roll     Roll      Yes
               4    Yes     Roll     Roll     Roll      Yes
               5    Yes      Yes      Yes      Yes      Yes
  Supercharger 1    Yes       No       No       No       No
               2    Yes       No       No       No       No
      Food Fight    Yes      Yes     Lock     Lock      Yes
 

Whether or not a given cart works on a given deck depends on both cart and deck. There's no real consistency among different carts of the same title. It looks like the Supercharger is the proof test of whether a given deck will be fully compatible with any 2600 cart. The conventional wisdom saying that a deck with the expansion port will work with anything is false. Presence or absence of the port is not a reliable indicator of compatibility with all 2600 carts. Likewise, the deck's geographical origin is not a reliable indicator. The one manufactured in China (#5) has fewer compatibility problems than the others, but it still has some. The oldest deck (#1) performed flawlessly in all tests. This is probably from the earliest production run, and was either sold in one of the limited test-markets or was warehoused until Atari Corp realized the home video game market was still viable.

The manufacturing standards of deck #1 are better than the others. All the major chips inside are all socketed instead of being soldered directly to the board. Some of the other decks also have had some minor factory patchwork performed. They occasionally have resistors bridging points where they were clearly not originally intended to be, i.e. soldered directly to a chip pin or placed on the underside of the board.

Wondering if that 7800 deck sitting in the thrift store could be one of the fully-compatible ones? There are some very minor externally visible differences between my deck #1 and the others. These may not be 100% reliable indicators, but they are conspicuously different.

The labels on the undersides of decks 2-5 have a box drawn around the serial number. Deck #1 has no box drawn. The serial number itself on deck #1 is different from the others. The "72R4BR" prefix is very much smaller than the rest of the number. "AT85037836" is one continuous string of black characters with no spaces, while on deck #2 (#3-5 are similar), "A1 76 5904610" does have the spaces, and the "76" is stamped in blue. The cart contacts of deck #1 have a definite copper color, while the contacts of the others have a silvery appearance.

Superchargers may be permanently damaged when used on the 7800. Try Robot Tank first and then proceed only if that cart works.

To make your later model 7800 electronically the same as the early model 7800, check out John Soper's 7800 Compatibility Fixes page.
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[+-^CrossBow^-]

This information was also before the extra timing circuit was really noticed as it you will see it isn't spoke of in the information above. I can tell you that disabling the extra timing circuit will bring back those Activision titles listed as not being compatible in addition to allowing it to work with the Supercharger as well. Although the main issue with the super charge has more to do with the cartridge sleeve. The super charger's pegs to open the 2600 dust door on the cart slot are static and not spring loaded. As a result, it is possible the supercharger was listed as not working because the cartridge port sleeve didn't allow for the super charger to sit down all the way enough for the cartridge to make proper contact.

 

This is also a problem with the activision carts although for a different reason. Activision PCBs in the cartridges are thinner than Atari PCBs. As a result, over time the activision games simple don't make good contact due to worn our cartridge connectors on the console.

 

Clipping capacitor C64 (usually green and looks like a resistor but is actually a ceramic banded capacitor) on one leg (I usually remove the right leg) from the PCB disables the extra timing circuit. That allows those activision titles mentioned to work again, but at the expense of no longer allowing 2600 Kung Fu master to work and also likely preventing 2600 Dark Chambers from working. I mention likely on Dark Chambers because I have disabled that on 7800s where that game would continue to work and play without issues. But Kung Fu master is always effected by this from my testing. Then again, the 7800 version is better anyway. 

 

That is why I say having the expansion port or not doesn't matter because if you have one that has issues with the games listed, it can be made to be more compatible very easily. 

 

Notice how the last two units in the list are later made and seem to have better compatibility? Towards late 87, it seems that Atari was using different components that no longer made the extra timing circuit needed as I've seen plenty of those revision boards with the circuit silkscreen and vias on the board, but with a factory installed 0Ω resistor in place of the 74lsxx that normally would have been there bypassing all of it. So even Atari essentially fixed this in later made 7800s on their own quietly in the background of things.

 

To answer the question about the Expansion port, I thought the video line on it was video input only to be mixed with the internal graphics of the system and not really a video out? I've not messed with the expansion port other than using its +5 via to power UAVs in some cases.

 

[+DrVenkman]

13 minutes ago, -^CrossBow^- said:

To answer the question about the Expansion port, I thought the video line on it was video input only to be mixed with the internal graphics of the system and not really a video out?

The schematic says "output" but I've never scoped either of my two units to see if that's accurate. I bet @CPUWIZ knows already. Speaking of, he hasn't been around lately. Hope he's okay. 

 

[+-^CrossBow^-]

44 minutes ago, DrVenkman said:

The schematic says "output" but I've never scoped either of my two units to see if that's accurate. I bet @CPUWIZ knows already. Speaking of, he hasn't been around lately. Hope he's okay. 

 

That would indicate then that the video overlay would have to take place within the Laserdisc device itself. Basically the LD player attached would be outputting all of the video at that point. Also explains why there is one for audio as that would get combined and mixed within the LD player along with, we assume, whatever audio from the LD player. One other thing is that it looks to only provide Maria LUM and color signals. But... if the signals are directly tied to the resistors, then... it should be possible to make an external UAV type device that indeed could be plugged into the expansion port. However, it doesn't look like TIA's color is in there so this would have been strictly for 7800 only use.

 

If the LD player device was to act as a passthrough, then 2600 games wouldn't have worked without the TIA color being pass along as well if I'm looking at this correct?

 

And you are correct about CPU. Was September 19th really the last time he was here when he posted in the thread on Kurt's passing?

 

[+DrVenkman]

2 minutes ago, -^CrossBow^- said:

If the LD player device was to act as a passthrough, then 2600 games wouldn't have worked without the TIA color being pass along as well if I'm looking at this correct?

I looks like composite video SHOULD be on pin 3, taken after the resistor ladder but before it goes to the RF modulator. 

[+-^CrossBow^-]

59 minutes ago, DrVenkman said:

I looks like composite video SHOULD be on pin 3, taken after the resistor ladder but before it goes to the RF modulator. 

I didn't state that better. I meant for use with a plug in UAV like device since the UAV requires the separate color signals. As the expansion port only provide the MARIA stuff it would still have to be ran separately inside the system. Still... Kinda like the idea of a UAV that you could plug onto the side or install in the xpansion port section as a dedicated add in. 

 

 

[+DrVenkman]

Just now, -^CrossBow^- said:

I didn't state that better. I meant for use with a plug in UAV like device since the UAV requires the separate color signals. As the expansion port only provide the MARIA stuff it would still have to be ran separately inside the system. Still... Kinda like the idea of a UAV that you could plug onto the side or install in the xpansion port section as a dedicated add in. 

 

 

For a 7800-only device, you could conceivably adapt the UAV(*) as a plug-in device for Expansion Port models. If you ALSO want the same quality from 2600 games, you're back to picking up signals with bodge wires and running a cable so might as well just install a UAV inside. But for 7800-only, it should be do-able. 

 

(*) In lieu of the UAV, you could take Mytek's freely-published video circuit that he designed from scratch for the 576NUC+ board. That circuit produced video that is absolutely spot-on comparable to a UAV and it's available for anyone to use and take advantage of. 

[RockLobster]

Found this thread in 2024...

 

Since the last post, has anyone created anything that took advantage or adapters of this 7800 expansion port?

 

Also it seems I have two 7800 consoles.  I assume to keep the one with expansion port...

[+DrVenkman]

38 minutes ago, RockLobster said:

Since the last post, has anyone created anything that took advantage or adapters of this 7800 expansion port?

 

Nope. Alas. 

[Shawn]

1 hour ago, DrVenkman said:

Nope. Alas. 

 

I made a one off MP3 player for it a long time ago. I'm sure I posted it here somewhere. Made it so when you powered up the console it played the "have you played atari today?" jingle along with the BIOS screen.

[+-^CrossBow^-]

1 hour ago, DrVenkman said:

Nope. Alas. 

And while I never did make a plug in type add on for UAV usage, I did come up with my mount boards to still make it easier to install them after this initial discussion. I'd forgotten about this until this was brought back up.

 

[CPUWIZ]

My project is coming back from the dead, this year.  What do kids say these days?  "Stay Tuned"?